encrypted.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (C) 2010 IBM Corporation
   4 * Copyright (C) 2010 Politecnico di Torino, Italy
   5 *                    TORSEC group -- https://security.polito.it
   6 *
   7 * Authors:
   8 * Mimi Zohar <zohar@us.ibm.com>
   9 * Roberto Sassu <roberto.sassu@polito.it>
  10 *
  11 * See Documentation/security/keys/trusted-encrypted.rst
  12 */
  13
  14#include <linux/uaccess.h>
  15#include <linux/module.h>
  16#include <linux/init.h>
  17#include <linux/slab.h>
  18#include <linux/parser.h>
  19#include <linux/string.h>
  20#include <linux/err.h>
  21#include <keys/user-type.h>
  22#include <keys/trusted-type.h>
  23#include <keys/encrypted-type.h>
  24#include <linux/key-type.h>
  25#include <linux/random.h>
  26#include <linux/rcupdate.h>
  27#include <linux/scatterlist.h>
  28#include <linux/ctype.h>
  29#include <crypto/aes.h>
  30#include <crypto/sha2.h>
  31#include <crypto/skcipher.h>
  32#include <crypto/utils.h>
  33
  34#include "encrypted.h"
  35#include "ecryptfs_format.h"
  36
  37static const char KEY_TRUSTED_PREFIX[] = "trusted:";
  38static const char KEY_USER_PREFIX[] = "user:";
  39static const char blkcipher_alg[] = "cbc(aes)";
  40static const char key_format_default[] = "default";
  41static const char key_format_ecryptfs[] = "ecryptfs";
  42static const char key_format_enc32[] = "enc32";
  43static unsigned int ivsize;
  44static int blksize;
  45
  46#define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
  47#define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
  48#define KEY_ECRYPTFS_DESC_LEN 16
  49#define HASH_SIZE SHA256_DIGEST_SIZE
  50#define MAX_DATA_SIZE 4096
  51#define MIN_DATA_SIZE  20
  52#define KEY_ENC32_PAYLOAD_LEN 32
  53
  54enum {
  55	Opt_new, Opt_load, Opt_update, Opt_err
  56};
  57
  58enum {
  59	Opt_default, Opt_ecryptfs, Opt_enc32, Opt_error
  60};
  61
  62static const match_table_t key_format_tokens = {
  63	{Opt_default, "default"},
  64	{Opt_ecryptfs, "ecryptfs"},
  65	{Opt_enc32, "enc32"},
  66	{Opt_error, NULL}
  67};
  68
  69static const match_table_t key_tokens = {
  70	{Opt_new, "new"},
  71	{Opt_load, "load"},
  72	{Opt_update, "update"},
  73	{Opt_err, NULL}
  74};
  75
  76static bool user_decrypted_data = IS_ENABLED(CONFIG_USER_DECRYPTED_DATA);
  77module_param(user_decrypted_data, bool, 0);
  78MODULE_PARM_DESC(user_decrypted_data,
  79	"Allow instantiation of encrypted keys using provided decrypted data");
  80
  81static int aes_get_sizes(void)
  82{
  83	struct crypto_skcipher *tfm;
  84
  85	tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
  86	if (IS_ERR(tfm)) {
  87		pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
  88		       PTR_ERR(tfm));
  89		return PTR_ERR(tfm);
  90	}
  91	ivsize = crypto_skcipher_ivsize(tfm);
  92	blksize = crypto_skcipher_blocksize(tfm);
  93	crypto_free_skcipher(tfm);
  94	return 0;
  95}
  96
  97/*
  98 * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
  99 *
 100 * The description of a encrypted key with format 'ecryptfs' must contain
 101 * exactly 16 hexadecimal characters.
 102 *
 103 */
 104static int valid_ecryptfs_desc(const char *ecryptfs_desc)
 105{
 106	int i;
 107
 108	if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
 109		pr_err("encrypted_key: key description must be %d hexadecimal "
 110		       "characters long\n", KEY_ECRYPTFS_DESC_LEN);
 111		return -EINVAL;
 112	}
 113
 114	for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
 115		if (!isxdigit(ecryptfs_desc[i])) {
 116			pr_err("encrypted_key: key description must contain "
 117			       "only hexadecimal characters\n");
 118			return -EINVAL;
 119		}
 120	}
 121
 122	return 0;
 123}
 124
 125/*
 126 * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
 127 *
 128 * key-type:= "trusted:" | "user:"
 129 * desc:= master-key description
 130 *
 131 * Verify that 'key-type' is valid and that 'desc' exists. On key update,
 132 * only the master key description is permitted to change, not the key-type.
 133 * The key-type remains constant.
 134 *
 135 * On success returns 0, otherwise -EINVAL.
 136 */
 137static int valid_master_desc(const char *new_desc, const char *orig_desc)
 138{
 139	int prefix_len;
 140
 141	if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
 142		prefix_len = KEY_TRUSTED_PREFIX_LEN;
 143	else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
 144		prefix_len = KEY_USER_PREFIX_LEN;
 145	else
 146		return -EINVAL;
 147
 148	if (!new_desc[prefix_len])
 149		return -EINVAL;
 150
 151	if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
 152		return -EINVAL;
 153
 154	return 0;
 155}
 156
 157/*
 158 * datablob_parse - parse the keyctl data
 159 *
 160 * datablob format:
 161 * new [<format>] <master-key name> <decrypted data length> [<decrypted data>]
 162 * load [<format>] <master-key name> <decrypted data length>
 163 *     <encrypted iv + data>
 164 * update <new-master-key name>
 165 *
 166 * Tokenizes a copy of the keyctl data, returning a pointer to each token,
 167 * which is null terminated.
 168 *
 169 * On success returns 0, otherwise -EINVAL.
 170 */
 171static int datablob_parse(char *datablob, const char **format,
 172			  char **master_desc, char **decrypted_datalen,
 173			  char **hex_encoded_iv, char **decrypted_data)
 174{
 175	substring_t args[MAX_OPT_ARGS];
 176	int ret = -EINVAL;
 177	int key_cmd;
 178	int key_format;
 179	char *p, *keyword;
 180
 181	keyword = strsep(&datablob, " \t");
 182	if (!keyword) {
 183		pr_info("encrypted_key: insufficient parameters specified\n");
 184		return ret;
 185	}
 186	key_cmd = match_token(keyword, key_tokens, args);
 187
 188	/* Get optional format: default | ecryptfs */
 189	p = strsep(&datablob, " \t");
 190	if (!p) {
 191		pr_err("encrypted_key: insufficient parameters specified\n");
 192		return ret;
 193	}
 194
 195	key_format = match_token(p, key_format_tokens, args);
 196	switch (key_format) {
 197	case Opt_ecryptfs:
 198	case Opt_enc32:
 199	case Opt_default:
 200		*format = p;
 201		*master_desc = strsep(&datablob, " \t");
 202		break;
 203	case Opt_error:
 204		*master_desc = p;
 205		break;
 206	}
 207
 208	if (!*master_desc) {
 209		pr_info("encrypted_key: master key parameter is missing\n");
 210		goto out;
 211	}
 212
 213	if (valid_master_desc(*master_desc, NULL) < 0) {
 214		pr_info("encrypted_key: master key parameter \'%s\' "
 215			"is invalid\n", *master_desc);
 216		goto out;
 217	}
 218
 219	if (decrypted_datalen) {
 220		*decrypted_datalen = strsep(&datablob, " \t");
 221		if (!*decrypted_datalen) {
 222			pr_info("encrypted_key: keylen parameter is missing\n");
 223			goto out;
 224		}
 225	}
 226
 227	switch (key_cmd) {
 228	case Opt_new:
 229		if (!decrypted_datalen) {
 230			pr_info("encrypted_key: keyword \'%s\' not allowed "
 231				"when called from .update method\n", keyword);
 232			break;
 233		}
 234		*decrypted_data = strsep(&datablob, " \t");
 235		ret = 0;
 236		break;
 237	case Opt_load:
 238		if (!decrypted_datalen) {
 239			pr_info("encrypted_key: keyword \'%s\' not allowed "
 240				"when called from .update method\n", keyword);
 241			break;
 242		}
 243		*hex_encoded_iv = strsep(&datablob, " \t");
 244		if (!*hex_encoded_iv) {
 245			pr_info("encrypted_key: hex blob is missing\n");
 246			break;
 247		}
 248		ret = 0;
 249		break;
 250	case Opt_update:
 251		if (decrypted_datalen) {
 252			pr_info("encrypted_key: keyword \'%s\' not allowed "
 253				"when called from .instantiate method\n",
 254				keyword);
 255			break;
 256		}
 257		ret = 0;
 258		break;
 259	case Opt_err:
 260		pr_info("encrypted_key: keyword \'%s\' not recognized\n",
 261			keyword);
 262		break;
 263	}
 264out:
 265	return ret;
 266}
 267
 268/*
 269 * datablob_format - format as an ascii string, before copying to userspace
 270 */
 271static char *datablob_format(struct encrypted_key_payload *epayload,
 272			     size_t asciiblob_len)
 273{
 274	char *ascii_buf, *bufp;
 275	u8 *iv = epayload->iv;
 276	int len;
 277	int i;
 278
 279	ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
 280	if (!ascii_buf)
 281		goto out;
 282
 283	ascii_buf[asciiblob_len] = '\0';
 284
 285	/* copy datablob master_desc and datalen strings */
 286	len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
 287		      epayload->master_desc, epayload->datalen);
 288
 289	/* convert the hex encoded iv, encrypted-data and HMAC to ascii */
 290	bufp = &ascii_buf[len];
 291	for (i = 0; i < (asciiblob_len - len) / 2; i++)
 292		bufp = hex_byte_pack(bufp, iv[i]);
 293out:
 294	return ascii_buf;
 295}
 296
 297/*
 298 * request_user_key - request the user key
 299 *
 300 * Use a user provided key to encrypt/decrypt an encrypted-key.
 301 */
 302static struct key *request_user_key(const char *master_desc, const u8 **master_key,
 303				    size_t *master_keylen)
 304{
 305	const struct user_key_payload *upayload;
 306	struct key *ukey;
 307
 308	ukey = request_key(&key_type_user, master_desc, NULL);
 309	if (IS_ERR(ukey))
 310		goto error;
 311
 312	down_read(&ukey->sem);
 313	upayload = user_key_payload_locked(ukey);
 314	if (!upayload) {
 315		/* key was revoked before we acquired its semaphore */
 316		up_read(&ukey->sem);
 317		key_put(ukey);
 318		ukey = ERR_PTR(-EKEYREVOKED);
 319		goto error;
 320	}
 321	*master_key = upayload->data;
 322	*master_keylen = upayload->datalen;
 323error:
 324	return ukey;
 325}
 326
 327enum derived_key_type { ENC_KEY, AUTH_KEY };
 328
 329/* Derive authentication/encryption key from trusted key */
 330static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 331			   const u8 *master_key, size_t master_keylen)
 332{
 333	u8 *derived_buf;
 334	unsigned int derived_buf_len;
 335
 336	derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
 337	if (derived_buf_len < HASH_SIZE)
 338		derived_buf_len = HASH_SIZE;
 339
 340	derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
 341	if (!derived_buf)
 342		return -ENOMEM;
 343
 344	if (key_type)
 345		strcpy(derived_buf, "AUTH_KEY");
 346	else
 347		strcpy(derived_buf, "ENC_KEY");
 348
 349	memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 350	       master_keylen);
 351	sha256(derived_buf, derived_buf_len, derived_key);
 352	kfree_sensitive(derived_buf);
 353	return 0;
 354}
 355
 356static struct skcipher_request *init_skcipher_req(const u8 *key,
 357						  unsigned int key_len)
 358{
 359	struct skcipher_request *req;
 360	struct crypto_skcipher *tfm;
 361	int ret;
 362
 363	tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
 364	if (IS_ERR(tfm)) {
 365		pr_err("encrypted_key: failed to load %s transform (%ld)\n",
 366		       blkcipher_alg, PTR_ERR(tfm));
 367		return ERR_CAST(tfm);
 368	}
 369
 370	ret = crypto_skcipher_setkey(tfm, key, key_len);
 371	if (ret < 0) {
 372		pr_err("encrypted_key: failed to setkey (%d)\n", ret);
 373		crypto_free_skcipher(tfm);
 374		return ERR_PTR(ret);
 375	}
 376
 377	req = skcipher_request_alloc(tfm, GFP_KERNEL);
 378	if (!req) {
 379		pr_err("encrypted_key: failed to allocate request for %s\n",
 380		       blkcipher_alg);
 381		crypto_free_skcipher(tfm);
 382		return ERR_PTR(-ENOMEM);
 383	}
 384
 385	skcipher_request_set_callback(req, 0, NULL, NULL);
 386	return req;
 387}
 388
 389static struct key *request_master_key(struct encrypted_key_payload *epayload,
 390				      const u8 **master_key, size_t *master_keylen)
 391{
 392	struct key *mkey = ERR_PTR(-EINVAL);
 393
 394	if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
 395		     KEY_TRUSTED_PREFIX_LEN)) {
 396		mkey = request_trusted_key(epayload->master_desc +
 397					   KEY_TRUSTED_PREFIX_LEN,
 398					   master_key, master_keylen);
 399	} else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
 400			    KEY_USER_PREFIX_LEN)) {
 401		mkey = request_user_key(epayload->master_desc +
 402					KEY_USER_PREFIX_LEN,
 403					master_key, master_keylen);
 404	} else
 405		goto out;
 406
 407	if (IS_ERR(mkey)) {
 408		int ret = PTR_ERR(mkey);
 409
 410		if (ret == -ENOTSUPP)
 411			pr_info("encrypted_key: key %s not supported",
 412				epayload->master_desc);
 413		else
 414			pr_info("encrypted_key: key %s not found",
 415				epayload->master_desc);
 416		goto out;
 417	}
 418
 419	dump_master_key(*master_key, *master_keylen);
 420out:
 421	return mkey;
 422}
 423
 424/* Before returning data to userspace, encrypt decrypted data. */
 425static int derived_key_encrypt(struct encrypted_key_payload *epayload,
 426			       const u8 *derived_key,
 427			       unsigned int derived_keylen)
 428{
 429	struct scatterlist sg_in[2];
 430	struct scatterlist sg_out[1];
 431	struct crypto_skcipher *tfm;
 432	struct skcipher_request *req;
 433	unsigned int encrypted_datalen;
 434	u8 iv[AES_BLOCK_SIZE];
 435	int ret;
 436
 437	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 438
 439	req = init_skcipher_req(derived_key, derived_keylen);
 440	ret = PTR_ERR(req);
 441	if (IS_ERR(req))
 442		goto out;
 443	dump_decrypted_data(epayload);
 444
 445	sg_init_table(sg_in, 2);
 446	sg_set_buf(&sg_in[0], epayload->decrypted_data,
 447		   epayload->decrypted_datalen);
 448	sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
 449
 450	sg_init_table(sg_out, 1);
 451	sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
 452
 453	memcpy(iv, epayload->iv, sizeof(iv));
 454	skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 455	ret = crypto_skcipher_encrypt(req);
 456	tfm = crypto_skcipher_reqtfm(req);
 457	skcipher_request_free(req);
 458	crypto_free_skcipher(tfm);
 459	if (ret < 0)
 460		pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
 461	else
 462		dump_encrypted_data(epayload, encrypted_datalen);
 463out:
 464	return ret;
 465}
 466
 467static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 468				const u8 *master_key, size_t master_keylen)
 469{
 470	u8 derived_key[HASH_SIZE];
 471	u8 *digest;
 472	int ret;
 473
 474	ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 475	if (ret < 0)
 476		goto out;
 477
 478	digest = epayload->format + epayload->datablob_len;
 479	hmac_sha256_usingrawkey(derived_key, sizeof(derived_key),
 480				epayload->format, epayload->datablob_len,
 481				digest);
 482	dump_hmac(NULL, digest, HASH_SIZE);
 483out:
 484	memzero_explicit(derived_key, sizeof(derived_key));
 485	return ret;
 486}
 487
 488/* verify HMAC before decrypting encrypted key */
 489static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 490				const u8 *format, const u8 *master_key,
 491				size_t master_keylen)
 492{
 493	u8 derived_key[HASH_SIZE];
 494	u8 digest[HASH_SIZE];
 495	int ret;
 496	char *p;
 497	unsigned short len;
 498
 499	ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 500	if (ret < 0)
 501		goto out;
 502
 503	len = epayload->datablob_len;
 504	if (!format) {
 505		p = epayload->master_desc;
 506		len -= strlen(epayload->format) + 1;
 507	} else
 508		p = epayload->format;
 509
 510	hmac_sha256_usingrawkey(derived_key, sizeof(derived_key), p, len,
 511				digest);
 512	ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
 513			    sizeof(digest));
 514	if (ret) {
 515		ret = -EINVAL;
 516		dump_hmac("datablob",
 517			  epayload->format + epayload->datablob_len,
 518			  HASH_SIZE);
 519		dump_hmac("calc", digest, HASH_SIZE);
 520	}
 521out:
 522	memzero_explicit(derived_key, sizeof(derived_key));
 523	return ret;
 524}
 525
 526static int derived_key_decrypt(struct encrypted_key_payload *epayload,
 527			       const u8 *derived_key,
 528			       unsigned int derived_keylen)
 529{
 530	struct scatterlist sg_in[1];
 531	struct scatterlist sg_out[2];
 532	struct crypto_skcipher *tfm;
 533	struct skcipher_request *req;
 534	unsigned int encrypted_datalen;
 535	u8 iv[AES_BLOCK_SIZE];
 536	u8 *pad;
 537	int ret;
 538
 539	/* Throwaway buffer to hold the unused zero padding at the end */
 540	pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
 541	if (!pad)
 542		return -ENOMEM;
 543
 544	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 545	req = init_skcipher_req(derived_key, derived_keylen);
 546	ret = PTR_ERR(req);
 547	if (IS_ERR(req))
 548		goto out;
 549	dump_encrypted_data(epayload, encrypted_datalen);
 550
 551	sg_init_table(sg_in, 1);
 552	sg_init_table(sg_out, 2);
 553	sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 554	sg_set_buf(&sg_out[0], epayload->decrypted_data,
 555		   epayload->decrypted_datalen);
 556	sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
 557
 558	memcpy(iv, epayload->iv, sizeof(iv));
 559	skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 560	ret = crypto_skcipher_decrypt(req);
 561	tfm = crypto_skcipher_reqtfm(req);
 562	skcipher_request_free(req);
 563	crypto_free_skcipher(tfm);
 564	if (ret < 0)
 565		goto out;
 566	dump_decrypted_data(epayload);
 567out:
 568	kfree(pad);
 569	return ret;
 570}
 571
 572/* Allocate memory for decrypted key and datablob. */
 573static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 574							 const char *format,
 575							 const char *master_desc,
 576							 const char *datalen,
 577							 const char *decrypted_data)
 578{
 579	struct encrypted_key_payload *epayload = NULL;
 580	unsigned short datablob_len;
 581	unsigned short decrypted_datalen;
 582	unsigned short payload_datalen;
 583	unsigned int encrypted_datalen;
 584	unsigned int format_len;
 585	long dlen;
 586	int i;
 587	int ret;
 588
 589	ret = kstrtol(datalen, 10, &dlen);
 590	if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
 591		return ERR_PTR(-EINVAL);
 592
 593	format_len = (!format) ? strlen(key_format_default) : strlen(format);
 594	decrypted_datalen = dlen;
 595	payload_datalen = decrypted_datalen;
 596
 597	if (decrypted_data) {
 598		if (!user_decrypted_data) {
 599			pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n");
 600			return ERR_PTR(-EINVAL);
 601		}
 602		if (strlen(decrypted_data) != decrypted_datalen * 2) {
 603			pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n");
 604			return ERR_PTR(-EINVAL);
 605		}
 606		for (i = 0; i < strlen(decrypted_data); i++) {
 607			if (!isxdigit(decrypted_data[i])) {
 608				pr_err("encrypted key: decrypted data provided must contain only hexadecimal characters\n");
 609				return ERR_PTR(-EINVAL);
 610			}
 611		}
 612	}
 613
 614	if (format) {
 615		if (!strcmp(format, key_format_ecryptfs)) {
 616			if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
 617				pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n",
 618					ECRYPTFS_MAX_KEY_BYTES);
 619				return ERR_PTR(-EINVAL);
 620			}
 621			decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
 622			payload_datalen = sizeof(struct ecryptfs_auth_tok);
 623		} else if (!strcmp(format, key_format_enc32)) {
 624			if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) {
 625				pr_err("encrypted_key: enc32 key payload incorrect length: %d\n",
 626						decrypted_datalen);
 627				return ERR_PTR(-EINVAL);
 628			}
 629		}
 630	}
 631
 632	encrypted_datalen = roundup(decrypted_datalen, blksize);
 633
 634	datablob_len = format_len + 1 + strlen(master_desc) + 1
 635	    + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
 636
 637	ret = key_payload_reserve(key, payload_datalen + datablob_len
 638				  + HASH_SIZE + 1);
 639	if (ret < 0)
 640		return ERR_PTR(ret);
 641
 642	epayload = kzalloc(sizeof(*epayload) + payload_datalen +
 643			   datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 644	if (!epayload)
 645		return ERR_PTR(-ENOMEM);
 646
 647	epayload->payload_datalen = payload_datalen;
 648	epayload->decrypted_datalen = decrypted_datalen;
 649	epayload->datablob_len = datablob_len;
 650	return epayload;
 651}
 652
 653static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 654				 const char *format, const char *hex_encoded_iv)
 655{
 656	struct key *mkey;
 657	u8 derived_key[HASH_SIZE];
 658	const u8 *master_key;
 659	u8 *hmac;
 660	const char *hex_encoded_data;
 661	unsigned int encrypted_datalen;
 662	size_t master_keylen;
 663	size_t asciilen;
 664	int ret;
 665
 666	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 667	asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 668	if (strlen(hex_encoded_iv) != asciilen)
 669		return -EINVAL;
 670
 671	hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 672	ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 673	if (ret < 0)
 674		return -EINVAL;
 675	ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
 676		      encrypted_datalen);
 677	if (ret < 0)
 678		return -EINVAL;
 679
 680	hmac = epayload->format + epayload->datablob_len;
 681	ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
 682		      HASH_SIZE);
 683	if (ret < 0)
 684		return -EINVAL;
 685
 686	mkey = request_master_key(epayload, &master_key, &master_keylen);
 687	if (IS_ERR(mkey))
 688		return PTR_ERR(mkey);
 689
 690	ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
 691	if (ret < 0) {
 692		pr_err("encrypted_key: bad hmac (%d)\n", ret);
 693		goto out;
 694	}
 695
 696	ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 697	if (ret < 0)
 698		goto out;
 699
 700	ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 701	if (ret < 0)
 702		pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 703out:
 704	up_read(&mkey->sem);
 705	key_put(mkey);
 706	memzero_explicit(derived_key, sizeof(derived_key));
 707	return ret;
 708}
 709
 710static void __ekey_init(struct encrypted_key_payload *epayload,
 711			const char *format, const char *master_desc,
 712			const char *datalen)
 713{
 714	unsigned int format_len;
 715
 716	format_len = (!format) ? strlen(key_format_default) : strlen(format);
 717	epayload->format = epayload->payload_data + epayload->payload_datalen;
 718	epayload->master_desc = epayload->format + format_len + 1;
 719	epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 720	epayload->iv = epayload->datalen + strlen(datalen) + 1;
 721	epayload->encrypted_data = epayload->iv + ivsize + 1;
 722	epayload->decrypted_data = epayload->payload_data;
 723
 724	if (!format)
 725		memcpy(epayload->format, key_format_default, format_len);
 726	else {
 727		if (!strcmp(format, key_format_ecryptfs))
 728			epayload->decrypted_data =
 729				ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
 730
 731		memcpy(epayload->format, format, format_len);
 732	}
 733
 734	memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 735	memcpy(epayload->datalen, datalen, strlen(datalen));
 736}
 737
 738/*
 739 * encrypted_init - initialize an encrypted key
 740 *
 741 * For a new key, use either a random number or user-provided decrypted data in
 742 * case it is provided. A random number is used for the iv in both cases. For
 743 * an old key, decrypt the hex encoded data.
 744 */
 745static int encrypted_init(struct encrypted_key_payload *epayload,
 746			  const char *key_desc, const char *format,
 747			  const char *master_desc, const char *datalen,
 748			  const char *hex_encoded_iv, const char *decrypted_data)
 749{
 750	int ret = 0;
 751
 752	if (format && !strcmp(format, key_format_ecryptfs)) {
 753		ret = valid_ecryptfs_desc(key_desc);
 754		if (ret < 0)
 755			return ret;
 756
 757		ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
 758				       key_desc);
 759	}
 760
 761	__ekey_init(epayload, format, master_desc, datalen);
 762	if (hex_encoded_iv) {
 763		ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
 764	} else if (decrypted_data) {
 765		get_random_bytes(epayload->iv, ivsize);
 766		ret = hex2bin(epayload->decrypted_data, decrypted_data,
 767			      epayload->decrypted_datalen);
 768	} else {
 769		get_random_bytes(epayload->iv, ivsize);
 770		get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen);
 771	}
 772	return ret;
 773}
 774
 775/*
 776 * encrypted_instantiate - instantiate an encrypted key
 777 *
 778 * Instantiates the key:
 779 * - by decrypting an existing encrypted datablob, or
 780 * - by creating a new encrypted key based on a kernel random number, or
 781 * - using provided decrypted data.
 782 *
 783 * On success, return 0. Otherwise return errno.
 784 */
 785static int encrypted_instantiate(struct key *key,
 786				 struct key_preparsed_payload *prep)
 787{
 788	struct encrypted_key_payload *epayload = NULL;
 789	char *datablob = NULL;
 790	const char *format = NULL;
 791	char *master_desc = NULL;
 792	char *decrypted_datalen = NULL;
 793	char *hex_encoded_iv = NULL;
 794	char *decrypted_data = NULL;
 795	size_t datalen = prep->datalen;
 796	int ret;
 797
 798	if (datalen == 0 || datalen > 32767 || !prep->data)
 799		return -EINVAL;
 800
 801	datablob = kmalloc(datalen + 1, GFP_KERNEL);
 802	if (!datablob)
 803		return -ENOMEM;
 804	datablob[datalen] = 0;
 805	memcpy(datablob, prep->data, datalen);
 806	ret = datablob_parse(datablob, &format, &master_desc,
 807			     &decrypted_datalen, &hex_encoded_iv, &decrypted_data);
 808	if (ret < 0)
 809		goto out;
 810
 811	epayload = encrypted_key_alloc(key, format, master_desc,
 812				       decrypted_datalen, decrypted_data);
 813	if (IS_ERR(epayload)) {
 814		ret = PTR_ERR(epayload);
 815		goto out;
 816	}
 817	ret = encrypted_init(epayload, key->description, format, master_desc,
 818			     decrypted_datalen, hex_encoded_iv, decrypted_data);
 819	if (ret < 0) {
 820		kfree_sensitive(epayload);
 821		goto out;
 822	}
 823
 824	rcu_assign_keypointer(key, epayload);
 825out:
 826	kfree_sensitive(datablob);
 827	return ret;
 828}
 829
 830static void encrypted_rcu_free(struct rcu_head *rcu)
 831{
 832	struct encrypted_key_payload *epayload;
 833
 834	epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 835	kfree_sensitive(epayload);
 836}
 837
 838/*
 839 * encrypted_update - update the master key description
 840 *
 841 * Change the master key description for an existing encrypted key.
 842 * The next read will return an encrypted datablob using the new
 843 * master key description.
 844 *
 845 * On success, return 0. Otherwise return errno.
 846 */
 847static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
 848{
 849	struct encrypted_key_payload *epayload = key->payload.data[0];
 850	struct encrypted_key_payload *new_epayload;
 851	char *buf;
 852	char *new_master_desc = NULL;
 853	const char *format = NULL;
 854	size_t datalen = prep->datalen;
 855	int ret = 0;
 856
 857	if (key_is_negative(key))
 858		return -ENOKEY;
 859	if (datalen == 0 || datalen > 32767 || !prep->data)
 860		return -EINVAL;
 861
 862	buf = kmalloc(datalen + 1, GFP_KERNEL);
 863	if (!buf)
 864		return -ENOMEM;
 865
 866	buf[datalen] = 0;
 867	memcpy(buf, prep->data, datalen);
 868	ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL, NULL);
 869	if (ret < 0)
 870		goto out;
 871
 872	ret = valid_master_desc(new_master_desc, epayload->master_desc);
 873	if (ret < 0)
 874		goto out;
 875
 876	new_epayload = encrypted_key_alloc(key, epayload->format,
 877					   new_master_desc, epayload->datalen, NULL);
 878	if (IS_ERR(new_epayload)) {
 879		ret = PTR_ERR(new_epayload);
 880		goto out;
 881	}
 882
 883	__ekey_init(new_epayload, epayload->format, new_master_desc,
 884		    epayload->datalen);
 885
 886	memcpy(new_epayload->iv, epayload->iv, ivsize);
 887	memcpy(new_epayload->payload_data, epayload->payload_data,
 888	       epayload->payload_datalen);
 889
 890	rcu_assign_keypointer(key, new_epayload);
 891	call_rcu(&epayload->rcu, encrypted_rcu_free);
 892out:
 893	kfree_sensitive(buf);
 894	return ret;
 895}
 896
 897/*
 898 * encrypted_read - format and copy out the encrypted data
 899 *
 900 * The resulting datablob format is:
 901 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 902 *
 903 * On success, return to userspace the encrypted key datablob size.
 904 */
 905static long encrypted_read(const struct key *key, char *buffer,
 906			   size_t buflen)
 907{
 908	struct encrypted_key_payload *epayload;
 909	struct key *mkey;
 910	const u8 *master_key;
 911	size_t master_keylen;
 912	char derived_key[HASH_SIZE];
 913	char *ascii_buf;
 914	size_t asciiblob_len;
 915	int ret;
 916
 917	epayload = dereference_key_locked(key);
 918
 919	/* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 920	asciiblob_len = epayload->datablob_len + ivsize + 1
 921	    + roundup(epayload->decrypted_datalen, blksize)
 922	    + (HASH_SIZE * 2);
 923
 924	if (!buffer || buflen < asciiblob_len)
 925		return asciiblob_len;
 926
 927	mkey = request_master_key(epayload, &master_key, &master_keylen);
 928	if (IS_ERR(mkey))
 929		return PTR_ERR(mkey);
 930
 931	ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 932	if (ret < 0)
 933		goto out;
 934
 935	ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 936	if (ret < 0)
 937		goto out;
 938
 939	ret = datablob_hmac_append(epayload, master_key, master_keylen);
 940	if (ret < 0)
 941		goto out;
 942
 943	ascii_buf = datablob_format(epayload, asciiblob_len);
 944	if (!ascii_buf) {
 945		ret = -ENOMEM;
 946		goto out;
 947	}
 948
 949	up_read(&mkey->sem);
 950	key_put(mkey);
 951	memzero_explicit(derived_key, sizeof(derived_key));
 952
 953	memcpy(buffer, ascii_buf, asciiblob_len);
 954	kfree_sensitive(ascii_buf);
 955
 956	return asciiblob_len;
 957out:
 958	up_read(&mkey->sem);
 959	key_put(mkey);
 960	memzero_explicit(derived_key, sizeof(derived_key));
 961	return ret;
 962}
 963
 964/*
 965 * encrypted_destroy - clear and free the key's payload
 966 */
 967static void encrypted_destroy(struct key *key)
 968{
 969	kfree_sensitive(key->payload.data[0]);
 970}
 971
 972struct key_type key_type_encrypted = {
 973	.name = "encrypted",
 974	.instantiate = encrypted_instantiate,
 975	.update = encrypted_update,
 976	.destroy = encrypted_destroy,
 977	.describe = user_describe,
 978	.read = encrypted_read,
 979};
 980EXPORT_SYMBOL_GPL(key_type_encrypted);
 981
 982static int __init init_encrypted(void)
 983{
 984	int ret;
 985
 986	ret = aes_get_sizes();
 987	if (ret < 0)
 988		return ret;
 989	return register_key_type(&key_type_encrypted);
 990}
 991
 992static void __exit cleanup_encrypted(void)
 993{
 994	unregister_key_type(&key_type_encrypted);
 995}
 996
 997late_initcall(init_encrypted);
 998module_exit(cleanup_encrypted);
 999
1000MODULE_DESCRIPTION("Encrypted key type");
1001MODULE_LICENSE("GPL");